1. Field of the Invention
This invention relates to a pneumatic radial tire for passenger cars, and more particularly to an improvement of a bead filler in the pneumatic radial tire for passenger cars which provides a good balance of cornering stability, riding comfort against vibration and noise by selecting appropriate properties of the bead filler without degrading general performance required in the tire of this type, particularly the cornering stability.
2. Description of the Prior Art
In this type of the pneumatic radial tire for passenger cars, it is required that a bead filler having an extremely high hardness and a substantially triangular shape in section be disposed between a carcass of a radial core structure and a turnup thereof wound around a bead core over a region extending from a position just above the bead core to a position substantially corresponding to a maximum width of the tire. The filler is employed in order to improve the cornering stability. In this connection, the use of the bead filler made of a superhard rubber stock is well-known, for example, from Japanese Utility Model Publication No. 47-16,084, French Patent Specification No. 1,260,138, U.S. Patent Specification No. 4,067,373 and the like.
Radial tires for passenger cars are known to have excellent riding comfort against vibration and noise and the like in addition to the cornering stability, unlike tires for truck and bus.
However, the cornering stability and the riding comfort against vibration are generally conflictive to each other. In the conventional radial tire for passenger car, therefore, either the cornering stability or the riding comfort is sacrificed, or both the performances are simply balanced at a low level.